Previous work on polyelectrolyte brushes has shown hydration profiles with greater swelling at the polymer-liquid interface than at the polymer-substrate interface. However, swelling behavior for polyeletrolyte brushes has rarely been studied in humid environments. This work utilizes X-ray reflectivity (XRR) and neutron reflectometry (NR) to investigate swelling profiles of the tertiary-amine bearing weak base poly(dimethylaminoethyl methacrylate) (PDMAEMA) after exposure to different relative humidity levels. Ellipsometry and XRR characterize the swelling behavior of the polymer brush while NR was used to assess the distribution of water (D2O) within the brush. We show that PDMAEMA brushes grown using surface-initiated ATRP swell extensively in humid environments at room temperature (graphic attached). Further work was performed to compare the swelling profile after quaternizing the tertiary amine with deuterated methyl iodide (CD3I). Utilizing CD3I in conjunction with NR allowed us to characterize two phenomena: 1) the quaternization profile as a function of depth in the brush and 2) the change in humidity uptake after quaternization. The results indicate a non-linear increase in swelling of the brush with increasing relative humidity before quaternization and an altered swelling character after quaternization. NR also shows a unique quaternization profile along the depth of the brush.

Water uptake and swelling of weak polyelectrolyte brushes in a humid environment

248th National Meeting (2014)

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